Portable electronic devices typically use a primary or secondary energy storage medium (battery) to derive power necessary for operation. A contacting scheme is required to connect the energy source with the electronic circuitry in the electronic device.
Many attempts have been made to design a contacting scheme that will provide reliable electrical contact during all modes of operation. An example of a more demanding mode is when the electronic device has been dropped. Any movement of the battery during the shock and vibration created by the impact of drop that causes a loss of power (the physical battery connection is broken), will cause unpredictable device operation, or in the case of a device with volatile memory circuits, a total loss of the memory's contents.
An important point which must be considered in the case of a miniature electronic device is that the mass of the battery is a majority of the total mass of the device. This creates problems in the design of a system to effectively retain the battery in a constant position during operation in all possible orientations and modes.
In general, the battery is located in a cylindrical chamber formed within the device's housing. To contact a AA battery, present embodiments require that conductive contacts be placed at opposite ends of the cylindrical chamber at or near the axis of the cylinder. Using conventional contacting methods, a conductive coil or flat leaf spring that compresses when the battery is inserted is situated at one end of the chamber. The spring force exerted by the contact acts to retain the battery against an opposing contact which is typically located on a sliding battery door. By using the sliding battery door for one of the contacts, the number of contact interfaces is increased to three. Interfaces are located between the spring terminal and battery, battery door and circuit board contact, and the battery door and battery.
The design objective for an optimal contacting scheme always dictates that the number of contact interfaces should be minimized. Following this objective will give a design with improved reliability as compared with a design having more interfaces.
Another problem with using the battery door to retain and contact the battery is that the spring loading, when applied to the battery door, will increase the stress and strain that must be supported by the battery door and its associated mounting hardware. This increased stress and strain will eventually lead to the deformation of the battery door and intermittent electrical contact performance.
Thus, what is needed is a means for reliably contacting an energy source used to power an electronic device.